Aphaniussplendens(KOSSWIG & SÖZER, 1945)

Classification

Distribution

Endemic to Lake Salda in the Turkish Lakes (Göller Bölgesi) region of the west Taurus mountains, southwestern Anatolia, Turkey. However the type specimens were collected from “Lake Gölcük” of which the precise location may be in question. Following several unsuccessful sampling trips in the last few decades most contemporary authors have considered it extirpated from a lake of that name close to the city of Isparta with a combination of pollution and introduction of the non-native, predatory zander (Sander lucioperca) usually blamed for its demise.

However the habitat and water conditions there are vastly different to those recorded in Lake Salda and it seems probable that the fish were actually discovered in a small, now dessicated area to the north of Lake Ak next to a settlement with the near-identical name Gŏlcük. This is much closer to Salda than Lake Gölcük and older maps clearly show a body of water at the location that is thought to have dried up in the not-too-distant past.

At any rate Lake Salda almost certainly contains the last remaining population and it has been considered critically endangered by the IUCN since 1996. See the ‘notes’ section for a little more on the distribution of Aphanius in Anatolia.

Habitat

Lake Salda is a highly alkaline, magnesium rich soda lake and the surrounding rock contains the mineral hydromagnesite which forms stromatolites (ancient, layered rock-like structures usually resulting from the activity of cyanobacteria and related organisms) all around the shoreline.

The water contains very high levels of dissolved salts (magnesium to 365 mg/L, calcium to 120 mg/L, chlorides to 1277 mg/L) and as a result possesses some interesting climatological characteristics. For example despite being situated at an altitude of 1180m above sea level it never freezes and in winter retains a relatively high temperature compared with the surrounding air. This often result in the formation of a dense layer of fog at the water surface during those months.

It’s mostly fed by groundwater but there are also several streams and springs above ground. The water level fluctuates on an annual basis due to evaporation and the removal of groundwater for irrigation but overall has dropped significantly over the last few decades resulting in the exposure of white ‘beaches’ and greater numbers of stromatolites. The pollution of groundwater via runoff from agriculture and domestic waste is also having a gradual effect on the chemical composition of the lake and represents a serious long-term threat to the survival of A. splendens. The introduction of carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) is also likely to be exerting pressure on native fish species.

Salda is considered oligotrophic and typical of such environments supports only limited diversity of zooplankton and phytoplankton. Higher aquatic plants are completely absent with the only vegetation consisting of diatoms, Cyanobacteria and other algae. These tend to grow most abundantly in shallower, littoral zones and it is here that the fish are found in the greatest numbers. Around the mouths of some streams they are found co-existing with populations of A. anatoliae which have been forced towards the lake due to the drying or pollution of surrounding waters. It appears that a degree of hybridisation has occured as a result.

Maximum Standard Length

Should be maintained as a larger group in a tank with base dimensions measuring upwards of 120 ∗ 30 cm.

Maintenance

Even for long-term maintenance a simple set-up will suffice. The most important factors are the provision of cover and a suitable medium in which the fish can deposit eggs. Much of the available space can therefore be filled with acrylic wool mops (use a fine grade if available) and ideally filamentousalgae.

Fine-leaved plants such as Java moss or Ceratophyllum can be used but may fail to thrive as the addition of marine salt to the water in the ratio of 2-3 g/L is necessary. Similarly there is no need to add a substrate although inert sand or gravel can be added if you prefer and filtration need not be too strong either. It is possible, and preferable, to maintain it outdoors all year round in many countries and it will show better colours and overall condition if exposed to at least a few hours of natural sunlight each day.

Water Conditions

Temperature: The water temperature in Lake Salda has been measured to vary between 6.5 – 22 °C over the course of the year. Artificial heating is not required in all but the coldest climates and it should be provided with a ‘winter’ period of several months during which it is maintained at low temperatures or it is likely to suffer both reduced fecundity and a shortened lifespan.

pH: The approximate pH value in the lake ranges between 8.0 – 10.0 and we suggest aiming for similar values in aquaria. It will probably not survive under acidic conditions.

Diet

Aphaniusspecies are basically micropredators feeding on small aquatic crustaceans, worms, insect larvae and other zooplankton although algae and other plant material is also taken at times. In the aquarium they will learn to accept dried foods in most cases but should also be offered regular meals of small live or frozen fare such as Artemia, Daphnia or bloodworm. This is particularly important during the months of spring and summer due to their high reproductive effort throughout this period. If the aquarium or container does not contain filamentousalgae try to introduce a good quality dried product with added Spirulina content to the diet.

Given its particular water requirements and precarious status in nature we strongly recommend maintaining it alone, the emphasis being on captive reproduction. Ideally it should be kept in a group with a ratio of two or three females to each male. Males are not as aggressive as those of most congenerics and several can usually be maintained together without problems.

Sexual Dimorphism

As with all members of the genussexual dimorphism is pronounced. Males exhibit a body pattern consisting of 8-11 highly variable, dark grey to black vertical bars with usually one or more dark bars in the caudalfin. The anal fin is white to yellow with a thin black edge and the dorsalfin also has a dark border. There may also be a series of dark spots on the head. Females are larger and much plainer possessing only a series of variable dark blotches on the flanks and completely hyaline finnage.

Reproduction

Captive reproduction is not difficult if the tank or container is properly arranged and maintained (see ‘tank set-up’) . It is a fractional spawner with females depositing eggs on a more-or-less continuous basis between the months of April and September. Males form temporary territories which they defend against rivals while attempting to entice females to spawn. Dominant individuals will show more intense colouration while the body of receptive females turns yellowish. Eggs are released singly or in small batches and are attached to algae or other surfaces by means of small filaments. Aphanius typically eat their eggs/fry and the medium should therefore be checked on a daily basis during the spawning period.

The eggs of this subspecies are the smallest among the genus and must be treated very carefully. Use a fine pair of forceps to gently remove pieces of medium with eggs attached whilst avoiding contact with the eggs themselves. Alternatively the entire medium can be removed and replaced every couple of days. The medium/eggs should be transferred to a container with water of the same chemistry and temperature as that of the adults. The incubation period can vary a little with the temperature but is usually between 15-17 days and the tiny fry will require an infusoria–type food for several days until large enough to accept Artemianauplii, microworm etc.

The elongated, slender body profile, angular lower jaw and reduced scalation exhibited by this little-known subspecies have seen it placed in the disused generaAnatolichthys and Kosswigichthys in the past and it’s still sometimes listed as a member of Lebias, though that name has long been considered a synonym of Cyprinodon by most authorities and an ICZN committee voted to suppress the name in favour of Aphanius as recently as 2003.

You’re unlikely to find it on sale in aquatic stores although it may be available via specialist breeders or associations from time-to-time. While Aphanius are certainly not as colourful as some of their relatives their interesting behaviour and continuous activity make them fascinating aquarium subjects and well worth a try if you possess the dedication to take on a long-term maintenance project since conservation is key with all members of the genus.

The Anatolia region represents a centre of diversity with ten endemicspecies described to date. These are thought to have diverged as a result of the splitting of what was originally a vast lake covering much of modern Anatolia. Two separate divergence events occured, the first resulting in the western separation of A. asquamatus, A. danfordii and A. villwocki around 12-15 million years ago (possibly earlier in the case of A. asquamatus).

Lakes Tuz, Eğirdir and Beyşehir are remnants of the central part of the lake where A. splendens now occurs and there also exist three other species in the Turkish Lakes region that were isolated when the eastern end of the lake became disconnected around 11-12 mya. They were further separated from one another 7-8 mya and have evolved independantly to survive in bitter lake environments containing high levels of alkaline carbonates and sulfates. Due to an historic lack of competition, predators and aquatic vegetation in their habitats they have developed distinctive limnetic (open water) characteristics including an elongated, relatively slim body shape and unique jawmorphology.

A. anatoliae is the most easily distinguished of this so-called A. anatoliaespecies complex as it’s the only fully-scaled member of the group – A. splendens, A. sureyanus and A. transgrediens all show differences in the extent of scalation on the body which is now known not to be a fixed characteristic and results from an unpredictable variation in their genes. It’s been hypothesised that this occured due to a lack of selective pressures allowing individuals with less scalation to survive and breed, thus facilitating an overall increase in scale variation.

This may represent a case of regressive evolution as neither the stream/river dwelling populations of A. anatoliae or other Anatolian Aphanius (fully-scaled) nor the very isolated A. asquamatus (completely scaleless) exhibit such variations. The relatively wide genetic variation among the isolated populations when compared with the riverine ones suggests that genetic flow is an important factor in the structure of Aphanius populations (Hrnek et al., 2002).

Further the lake district species can interbreed freely in aquaria and appear to form a distinct clade whereas the forms found in western and central Anatolia have been shown to exhibit differing degrees of sterility to the lake fishes. When this is considered problems with nomenclature arise and Villwock (2004) theorised that all subpopulations should be regarded as “speciesin statu nascendi” i.e. in the process of creation and referred to as A. anatoliae ssp. pending further study. Hrnek et al. (2002) alternatively suggested that the different clades may represent new species but agreed that further study is required. We’ve chosen to list them separately in order to avoid using sub-specific names.

The genus currently contains 22 species and subspecies which are thought to have derived from a common ancestor originally distributed around the periphery of the former Tethys Sea. None are particularly well-documented in aquarium literature although some are very beautiful and the majority are not too difficult to maintain and breed. Sadly most are on the verge of extinction for one reason or another with several existing only in remnant, highly-localised populations. In practically all cases the root cause for this decline is the activity of humans and although some species are now protected by conservation law the mismanagement and degradation of their habitats continues at an alarming rate.